Hazardous location plugs and receptacles are typically used in hazardous areas where power is to be supplied to electrical equipment, such as compressors, motors, motor-generator sets, tools, lighting systems, and similar devices. The plugs and receptacles may be used, for example, in military applications, aerospace applications, damp or corrosive areas, armored applications, on board ships, or in other harsh or hazardous environments.
Conventional receptacles for use with hazardous location plugs typically include a rotatable locking plate adapted to receive the contact pins of the plug, contacts positioned behind the locking plate and within the receptacle, and a number of fixed key portions surrounding the locking plate. The hazardous location plug is inserted into the locking plate completely. The plug is then rotated in a clockwise direction to engage the internal contacts of the receptacle and to complete an electrical circuit.
Conventional hazardous location plugs also include grooves that fit over the fixed key portions of the receptacle. Once the plug is inserted into the locking plate and the locking plate is depressed and rotated, the plug is locked into place via a ledge on the fixed key portions positioned in the grooves. The locking of the plug in place helps prevent accidental disengagement (which could lead to sparking) of the plug from the receptacle.
To safely disengage the hazardous location plug from the hazardous location receptacle, the plug must be rotated in a counter-clockwise direction to disengage the plug's contact pins from the receptacle contacts and to break the electrical circuit. Any sparking that may occur from the break in the electrical circuit is confined within the receptacle. In addition, the fixed key portions do not lock the plug in place upon rotation in the counter-clockwise direction. The plug can then be removed from the locking plate of the receptacle.
One deficiency in the design of conventional hazardous location receptacles is that any standard plug may be inserted into the receptacle. Similar to the insertion of hazardous location plugs into the receptacle, standard plugs can be inserted into the locking plate, and the locking plate can be depressed and rotated to contact the contacts in the receptacle. The difference, however, is that standard plugs generally have a smaller diameter than hazardous location plugs and lack the grooves that fit over the fixed key portions to lock the plug in place. Therefore, standard plugs can easily be pulled out of the receptacle, which could lead to sparking and result in an explosion.
Therefore, a need exists in the art for a receptacle that can prevent the use of non-hazardous location plugs with a receptacle in hazardous areas.